1. Field of the Invention
The present invention relates to an electroless copper plating solution, a method of producing the same, and an electroless copper plating method, and, more particularly, to an electroless copper plating solution including a copper salt, a complexing agent, a reductant and a pH adjuster, in which the plating solution includes a 2,2-dipyridyl acid solution and the hydrogen ion concentration (pH) thereof is about 11.5 to about 13.0, a method of producing the same, and an electroless copper plating method.
2. Description of the Related Art
In electronic devices such as integrated circuit (“IC”), liquid crystal displays (“LCD”) and the like, as the degree of integration increases and the size decreases metal wiring, which must be formed on a substrate, is commensurately miniaturized. Accordingly, the cross-sectional area of the metal wiring decreases, and the total length of the metal wiring increases, so that the net resistance of the metal wiring is substantially increased overall. The increase in resistance in the metal wiring of display devices causes the display quality of display devices to deteriorate due to signal delay. This delay can become problematic, particularly for the development of high image quality and large sized TFT-LCDs. Accordingly, it is desirable to decrease the resistance of metal wiring.
Copper as a conductive material has relatively low specific resistance and excellent electromigration resistance. Accordingly, when copper is used for wiring, it is desirable that current carrying capacity will remain unchanged in proportion to miniaturization and high integration density of the smaller devices. Suitable methods of forming copper wiring include electroless plating which is a method of plating a metal film by the reaction of between a reductant and an oxidant in solution to provide the metal at the surface of an activated substrate. Advantageously, since the electroless plating method does not require formation of an additional seed layer, and is performed uniformly and simultaneously throughout the entire substrate without using an external power source, the deterioration of uniformity due to the current-resistance (“IR”) drop is improved, the manufacturing cost is low, processes are simple, and thus productivity is high.
Generally, an electroless copper plating solution includes a source of copper ions, a complexing agent for copper ions, a reductant for copper ions, and a pH adjuster. When copper plating was performed using the electroless copper plating solution, obtaining a plating film having high adhesion was difficult, the speed of forming a metal plating film was low, and uniform plating of the entire substrate was difficult.
Various additives can be added to a plating solution for electroless copper plating, so as to improve the stability and material properties of the plating solution and the characteristics of the copper pattern formed therefrom. For example, Japanese Unexamined Patent Application Publication No. sho52-17334 discloses an electroless copper plating solution containing one or more additives selected from the group consisting of murexide, eriochrome black T, and methyl violet. Further, Japanese Unexamined Patent Application Publication No. sho52-17335 discloses an electroless copper plating solution containing, as an additive, one or more selected from the group consisting of pyridine, 4-vinylpyridine, 2-aminopyridine, 2-methylpyridine, 3-methylpyridine-4-methylpyridine, 2-ethylpyridine, 3-(n-propyl)pyridine, and 2-hydroxypyridine. However, neither of these conventional electroless plating solutions can provide a copper film that exhibiting both sufficiently low electrical resistance and excellent adhesivity.